LED UV, is it a farce, lets discuss

dallasg

dallasg

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So here is my debate for the weekend, after speaking to people in the LED unit market, doing some research, reading and some logic: is there any use for UV in corals.

LED unit hype is all about UV now and yet I can't find anything showing the need, seen a few articles where chlorophyll stops above UV, T5 globes don't emit UV and we filter it out from Metal Halides, have I missed something

Will post links once we get a discussion going
 
following as the vertex unit has brought out UV pads and I would also like to know what the benefits are?????
 
Well I am waiting for permission to post replies I have, and getting more info from the experts like Sanjay Joshi
 
Which UV are we going to talk about UV-A UV-B UV-C or UVR.....

Glass shields in halide lights only shelled out UV-B and UV-C. UV-C is the UV used in UV steriliser units. So I assume we talk about UV-A and UVR.
 
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Well that I leave for discussion, yes UV-A is what we want
Lets get the creative juices flowing
 
When I first joined MASA Rob and I had a discussion on the manipulating of coral colour by changing the UV spectrum. Most zooxanthellae produce UVR blocking pigments. These pigments (colour) change when the UV wave length changes. It is thought that most corals use the wavelength between 350 and 400nm Some say the band is a lot narrower 360 - to 380nm.
 
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Here is a reply I got
UV light can be dangerous to all biological life including us humans so we will first explain the different wavelengths of UV light and their effects.

UV-A – 315-400nm
UVA is the most commonly found form of UV, and is responsible for the tanning effect we see in our skin after time spent in sunlight. UV-A can cause sunburn if exposure is excessive and the atmosphere does very little to block this range of UV.

UV-B – 280-315nm
UVB is the most dangerous of all forms of UV light. It possesses enough energy to wreak havoc on cellular DNA cells but not enough to be absorbed by our atmosphere like UV-C.
Overcast or cloudy skies are not enough protection from this type of UV light.

UV-C – 200-280nm
This light is relatively safe to us because our atmosphere absorbs these rays. UV-C is found on germicidal lamps and UV sterilizers where it will destroy any biological life it comes in contact with.
Click to expand...
 
viper357 said:
What is UV-A and why do we want it?
Click to expand...

Corals produce pigments like blue, purple and pink to protect their DNA and RNA, which is damaged by UV-A and UV-B.
 
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Also, the deeper you go, the more UV is absorbed.
 
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More
Is UV Light Safe For Corals?
The answer is yes and it is beneficial to corals providing it is emitted at safe levels. Metal halide and especially HQI lamps all emit much UV-A and must be filtered out by a glass or acrylic cover or corals face the possibility of bleaching as the Zooxanthellae cannot adjust to this light at a very fast pace. Since corals need sunlight to make food, most live in shallow waters near the ocean’s surface which exposes them to UV-A and UV-B rays. Fortunately corals have the ability to make their own sunscreen to protect them and allow only high and safe ranges of UV which is beneficial to the Zooxanthellae that reside in the corals which provide food to them by way of photosynthesis. This is one of the concerns with our ozone layer slowly being reduced. The ozone filters out the dangerous UV-C rays which would otherwise kill the corals as they cannot produce enough sunscreen to protect them from these type UV rays.

Unlike metal halide lamps, LEDs in the 400-700nm range that are used in aquarium fixtures do not emit UV radiation and that is one of the reasons Orphek now incorporates high range UV-A LEDs in their systems. The beauty of this is that unlike metal halide/HQI lamps, the UV-A output can be controlled thereby providing safe and beneficial levels for the corals while still bringing out the beautiful fluorescence of the corals. Orphek’s UV LEDs are in the range of 380-400nm which enters the visible range which produce a small amount of UV yielding a bluish purple light causing the corals to fluoresce while improving photosynthesis within the corals.
Click to expand...
 
UV-A is from 320 - 400nm
UV-B is from 280 - 320nm
UV-C is from 200 - 280nm

UVR is uv radiation

Most UV-C is filtered out by the ozone layer and does not reach the reefs or earth. This UV is used for sterilisation etc

Some UV-B reaches the reefs but it is filtered out by glass and water. Very small amounts reach the corals.

UV-A reaches the corals and the pigments in the Zooxanthellae shield the coral. Too much UV and the coral burns to little and the zooxanthellae bleaches.

This is where I think Dallis is hoping this thread will head.
 
Ok so here is another question, why do units that don't contain UV leds, and if they are strong enough, why does that also bleach corals?
 
And T5's with no UV also grow corals well
 
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